FAQ for using bioreporters in the field

As discussed with a member of the EPFL communication team, we came up with an FAQ about the bioreporter and genetically modified organisms in general (GMO). We would like to express our thanks to Prof. Van der Meer from the Department of Fundamental Microbiology at UNIL and Dr. Sabrina Leuenberger from the University of Bern for their help in putting up this FAQ.

Q: What is the accepted amount of arsenic in drinking water?

A: 10 ppb (µg/L)

The World Health Organization has set 10 ppb (μg/L) for most countries, with the exception of 50 ppb for locations with high amounts of arsenic. Arsenic can be found in groundwater as a result of natural weathering and microbial processes, but also due to industrial and mining contamination.

Q: Why do we care about arsenic?

A: Chronic exposure can cause cancer.

The connection with cancer is now being re-visited, with correlation to skin, bladder, kidney, lung and other cancer risks. The 50 ppb standard represents more than 2000 times the risk for cancer in the lifetime compared to other known carcinogens (benzene, tetrachloroethylene, DDT, PCB). Before cancer, there are visible symptoms on the skin, and alteration in liver and kidney functions. Acute symptoms that can lead to death are likely due to exposure to high amounts of inorganic arsenic.

Q: Why detect arsenic with a bioreporter?

A: Because assays with bioreporters are cheap and easy, and can be used in the field. They do not produce toxic metal waste like chemical field test kits for arsenic detection.

Assays with bioreporters produce an easily detectable signal, such as fluorescence, color, electricity or luminescence. Assays do not produce toxic gases or require expensive reagents or machines (such as the atomic absorption spectroscopy) for the detection to work. Bioreporters for arsenic have a very low detection limit, and both laboratory and field experiments have shown that as little as 1 ppb of Arsenic can be detected in an aqueous sample.

Q: What is a bioreporter?

A: A living organism that produces a signal when it detects a target chemical.

The term bioreporter mostly refers to an intact living microbial cells, but can also refer to higher organisms (zebrafish, plants, etc.), that have been genetically engineered to produce a detectable “reporter” signal when they have been in contact with a specific target compound.

Q: What is a Genetically Modified Organism (GMO)?

A: An organism in which one or more genes have been introduced or modified by means of DNA recombinant technology.

A genetically modified organism is an organism whose genetic material has been altered using genetic engineering techniques. It involves the deletion, insertion or mutation of genes in an organism.

Q: Since when do we do genetic modifications?

A: When we started breeding animals and plants for our interests

Biotechnology has been used by humans since the beginning of time. The first cases date from 12’000 BC when plants or animals were selectively breeded to keep only the ones with the specialities in which we were interested. Gene technology for making genetic modifications has been used roughly since the 1980’s.

Q: What is this antibiotic resistance?

A: When an antibiotic no longer works to kill bacteria or inhibit their growth

It is a form of drug resistance where a specific group of microorganism, usually bacteria, is able to survive after exposure to a specific antibiotic. Some antibiotics are frequently used in the laboratory to select for the maintenance of DNA fragments introduced by gene technology. Also the arsenic bioreporter bacterium carries a gene for kanamycin (an antibiotic) resistance. This gene is present on the same DNA fragment that contains the genes for the arsenic reporter. By adding kamamycin to the growth medium of the cells, we ensure that the reporter construct is maintained. Cells that have lost it are sensitive to kanamycin and will die.

Q: Can this genetic material be transferred to other bacteria?

A: In principle yes, but in practice not very efficiently.

Bacteria have a variety of ways by which they can exchange genetic material between different species. Therefore, in principle, the reporter DNA fragment with the kanamycin resistance gene could transfer from the reporter cells to some other bacterium in the environment. For this to happen, the reporter cells would have to escape, to die and to release their DNA. Another bacterium would then have to take this DNA up and stick it in its own genome. This scenario is not impossible, but the likelihood of it to happen depends on many factors. The major “risk” here is that the gene for kanamycin resistance would be taken up by another bacterium, and may spread to pathogenic bacteria. These could become resistant to kanamycin, which would then become ineffective in clinical settings. On the other hand, kanamycin is not in clinical use, which reduces the negative impact if, accidentally, the above-mentioned scenario would take place. Still, there is every reason to avoid as good as possible that the reporter bacteria can escape.

Q: What if accidentally, there is an accident with a bioreporter assay and the living bacteria are introduced in the environment?

A: They will most likely die.

Most environments are not favorable for growth of the Escherichia coli -based bioreporter bacteria. There are many other bacterial species present, and E. coli will have to compete to survive and will not have an advantage over other bacterial species. Therefore it will not survive very long – depending on the studies, in 1~4 weeks and only 1 in 100,000 bacteria survive. For a detailed description, see: The Risk Assessment of Arsolux in this article.

Q: What if we accidentally touch it, drink it, breath it?

A: Nothing will happen.

E. coli is a bacteria that is actually present in our gut. The bioreporter is based on a world-wide used laboratory strain K12, chosen for its absence to cause human disease. In addition, the strain has several genetic defects that minimize its growth outside the laboratory. This strain has been tested for survival in humans and animals and cannot survive more than 1 week. If the bacteria are ingested by accident, it can effectively be eliminated by other antibiotics available in the market, (with the exception of kanamycin but this is severely toxic for humans and not in direct clinical use).

Q: Can we find your notification on the BAFU (Federal Office for the Environment, Switzerland) website?

A: No.

The list of all notifications is not publicly listed on the BAFU website. We have made a public post that you can read here

Q: Is Arsenic the only thing detectable by the bioreporter?

A: No.

Antimony can also activate the same bioreporter, and iron and other compounds can inhibit the bioreporter. So proper controls must be made to understand the bioreporter signal.

We also have bioreporters for other heavy metals, such as mercury, cadmium or zinc, and for oil-spill related compounds, such as alkanes, solvents and polycyclic aromatic hydrocarbons.

Q : In specific conditions, could the bacterium accidentally start dividing and growing its population out of control ?

A: Most likely not

See the answer to “What if accidentally, there is an accident with a bioreporter assay and the living bacteria are introduced in the environment??”. The only reason why “escaped” bacteria would grow “out of control” is when they find abundant food sources that are not used by other bacteria. Fortunately, in and on our bodies, and in the environment, this is not the case. Bacteria exist everywhere and, as a consequence, food is limited in all ecosystems. The other bacteria in the “microbial community” keep invaders in check. If, however, we change conditions in the environment so that we would kill or inhibit all other bacteria, then invaders may get a chance to proliferate. This is thus a good reason not to overuse antibiotics or release them in the environment, which could create selective conditions for strains that are resistant to such compounds.

Q : If your technique proves being so efficient, it will inspire many other similar devices. How to make sure that they’ll all be as safe and carefully prepared as yours?

A: Each design will have to be approved for safety.

This device is approved with a very specific vial known for containment. If we change any part of the design, the design will have to be approved in Switzerland. This will be the same in other countries. The bacterial strains used to make the bioreporters are standardized strains. Bioreporters can be other organisms, not only bacteria. Most importantly, one of the main ideas of our project is to build a collaboration between the citizen scientist and a local university or hospital.